MHT CET Chemistry Question (2026) — Solution

Step-by-step solution

In a lead accumulator acting as a galvanic cell (discharging), the positive electrode acts as the cathode where reduction takes place. The reaction at the positive electrode is: PbO_2(s) + SO_4^ 2- (aq) + 4H^+(aq) + 2e^- PbSO_4(s) + 2H_2O(l) The oxidation state of Pb in PbO_2 is +4. The oxidation state of Pb in PbSO_4 is +2. The oxidation number of Pb changes from +4 to +2, which means it decreases by 2. Answer: decreases by 2